Contents

Reasoning

Shaded streets, footways, benches, bus stops, and other features are much more pleasant to use on a mid-summer day than similar features lacking shade. People often will forgo sitting on a bench at a bus stop in order to stand in the shade cast by the shelter roof if the sun angle places the bench in the sun. During winter, people may prefer to avoid shade and stand in the sun for warmth.

The purpose of this tag is to record whether a feature has shade during the heat of the day, so that the information can be used for routing. One of the developers of OpenTripPlanner has expressed interest in using shade as a routing criterion for walking, and thinks it it would take less than a dozen lines of code to do so.

While shade could be tagged as a simple yes/no, there is some value in knowing the source of the shade. For example:

the roof of a shelter at a bus stop will cast a small area of shade that will move as the day progresses, leaving the shelter itself unshaded for much of the day, and forcing patrons to choose between standing in the shade or sitting on an unshaded bench. On the other hand, if the bus stop is shaded by trees with broad canopies, shade may be continuous throughout the entire day. Tagging shade=roof for the bus stop would indicate that there is a roof (and shelter during rain), but tagging shade=trees would indicate a shadier stop; the apparent conflict for tagging bus stops with shelters and shaded by trees is easily resolved by tagging shelter=yes, shade=trees.

Shade trees provide additional cooling via transpiration.

Long porticoes, such as those in Turin, Italy, can provide cooling via the thermal mass of the structure.

Pergolas provide an element of visual delight and perhaps, depending on plantings, fragrance.

As 3-D modeling becomes more common within OpenStreetMap, shade could become a calculated attribute, using position, dimensions of structures and trees, season of year, and time of day. However, for the foreseeable future it will be more practical to record shade as an attribute of features that are shaded.

Rendering

It is not anticipated that shade would be rendered in the main OpenStreetMap renderers, although specialized applications might do so.

Tag values

The node or way is shaded by trees during the middle of a summer day. For a node, this could be by a single tree. A footway or other way should be tagged with shade=trees only if there is reasonably complete shade along its length.

The node or way is shaded by some other impervious structure (awning, roof, or similar canopy other than a portico) capable of providing shade and shelter from rain. If a way runs beneath an archway or tunnel through a building, code the walkway with “breezeway=yes” instead of “shade=roof.”